Looking at the supported API's for various camera both within the PDF docs and the supported cameras page (https://developer.sony.com/develop/cameras/), it looks like the A7R supports changing f stop, shutter speed, ISO, etc. However, within the iOS sample app none of those commands are provided by the camera as being available via the getAvailableApiList command. "Forcing" a setIsoSpeedRate command to the camera didn't work either and I get an error code 403: Forbidden.
So is this supported? Am I missing something? Does the camera need to be configured in a particular way? Of note, I am running firmware 1.10 on the A7R, which I believe is the latest.